Leg prosthesis



LEG PRs'mEsis Filedl Feb. 2, 1954 1N VENTOR.

AGT

United States Patent lice LEG PROSTHESIS Felix Kleinekathfer, Endorf, Upper Bavaria, Germany Application February 2, 1954, Serial No. 407,782

Claims priority, application Germany February 3, 1953 s claims. (Cl. 3-27) This invention relates to a leg prosthesis, especially a leg prosthesis which is equipped with a pressure-controlled knee-joint brake.

As far as the control of the movements of an articial leg during use is concerned, my Patent No. 2,588,013, March 4, 1952, is concerned with a portion only of the whole range of operation, namely, that during which the leg is moved into contact with the ground and, thus, is placed under pressure.

My present invention aims at the control of the operation of a leg prosthesis within the rest portion of the functions of the leg. More specically, my invention has for one of its objects the control of the use of the leg v prosthesis during the swinging motions of the shank of the leg.

With my invention applied to the artificial leg of the above referred to patent, it will be possible to control the whole range of possible functions.

While suggestions have already been made to eliminate 'I or at least to lessen the danger of unintended bending or of `a collapse of knee-joints when pressure is applied, the known artificial legs still have serious disadvantages which make themselves particularly felt when the leg is out of contact with the ground, that is, during the forward swinging movement of the shank. These shortcomings influence the entire sequence of movements and even the condition during the application of pressure. The main dilliculty consists in the fact that at the beginning of the swinging action when the articial limb, with no pressure or load applied, is swung forward, the shank, due to its weight and inertia, does not follow the forward movement of the thigh fast enough for normal walking. As a consequence, the shank and foot remain too far behind, causing the knee-joint to bend through 'an excessive angle, which makes the movement of the leg appear unnatural. It has also been suggested to reduce the undesired movement of Vthe shank by locating the center of rotation of -the knee-joint so that the center of gravity of the shank is -moved forwardly, or by providing elastic webbing or springs to favor the outstretched position of the leg in the knee-joint. l

The known devices to minimize the undesirable shank movement, and especially the known elastic members used for this purpose, have the disadvantage of acting too strongly in the lirst phase of the swinging movement and too weakly in the second phase. The same is true for the mentioned shift of the center of gravity of the shank. It with the known devices the swinging movement is adjusted for a certain moderate walking pace, such adjustment is no longer correct when the wearer of the artificial leg increases or reduces the rate of movement. If he, for instance, slows down, the shank will move forward too strongly and will hang stily from the kneejoint. if, on the other hand, the walking speed is increased above the average, the shank will not move for- -ward fast enough to support the load of the body, so 'that the knee-joint may collapse and the wearer may drop to the ground.

The primary object of my invention is to overcome the above referred to disadvantages and to provide, as has already been indicated, a leg prosthesis having an improved control mechanism for the swinging movements of the leg.

Other objects of the invention center about an artificial leg having a mechanism as referred to, which will reliably control the forward motion of the shank during walking regardless of the speed of walking, which will cause the shank to swing easily andy naturally within the desired space at theslowest walking speed, and will prevent the shank, even during fastest walking, from swinging too far backwards.

A further object of this invention is to provide a leg prosthesis having a control mechanism for the swinging motions of the leg, which mechanism will urge the shank, when bent backwards with respect to the thigh, into the outstretched legv position to be ready for the support of the load. v

One 'object of the present invention is to apply my new control mechanism for the swinging motions of an articial leg to a leg which is equipped with a pressure-controlled knee-joint brake.

Still another object of the invention is a device which will increase the braking effect of a conventional kneejoint brake.

In accordance with the present invention, the above indicated objects, as well as those objects which will hereinafter appear, are achieved by providing inan artificial leg, including a thigh and a shank, a resilient connection between the thigh and the shank which will control the swinging motion of the shank, and limitthe swinging movement, first by counterbalancing the gravity which pulls the shank forward, or by even favoring a slightly bent position of the shank. The connection will become more eiective during further bending up to a certain bending angle, preferablyabout 150, and will exert a steadily increasing counterpressure upon continued bending. T he counterpressure ceases on further forcible bending below a certain angle, preferably bout and then causes bending. ,f

With my present auxiliary braking mechanism applied to an artificial leg provided with a pressure-controlled knee-joint brake, as shown in my Patent 2,588,013, the slightly eccentric brake surface of the thigh produces an increasing friction with the braking surface of the shank, as the outstretched condition is approached.

In order that the present invention may be fully under-- stood, illustrative embodiments are hereinafter described ,n

in detail, merely by way of example, and shown in the accompanying drawings wherein:

Fig. 1 is a fragmentary vertical section through an artificial leg embodying features of the invention, the leg being shown in outstretched condition;

Fig. 2 is a View similar to that of Fig. l, but showing tige prosthesis with its knee bent at an angle of 30 or 1 0;

Fig. 3 illustrates still another condition of the leg, the knee being bent beyond 90;

Fig. 4 illustrates a modiled artificial leg; and

Fig. 5 illustrates a detail.

Referring to the drawings, and initially to Figs. 1 t0 3, the knee end portion 1 of the thigh of an artificial leg has jointed thereto for pivotal movements a rod 2. This rod projects into a cavity in the calf of the shank 3 and is guided in an eye 4 of a guide 6 secured to the shank. Even with the thigh in its extreme angular position, the rod 2 cannot slide out of the eye 4. Above the eye 4, the rod 2 isprovided with a ange 5. BetweenA the guide 6 and the ange 5, there is a resilient member on .the rod 2. While a rubber buffer 7 is shown as a resilient Patented Oct. 22, 1957 member `in the. embodiment .of `the invention,selectedr for illustration, it will be clear -that a spring or any other resilient means may be employed instead of the rubber buffer. i

In the outstretched `condition ofA the legwthe rubber buffer is so far away from the guide r-that the thigh may beJ bent through-'approximately lE0,-asshown in Fig-2, or through a smaller or larger angle, `depending-on-the arrangement,--before -the-rubber buffer, upon -fur-thcr bending of the leg, will `be compressed (see Fig. 3). Thus, a .certain bending anglemaygbereached by a `freely swingmg pendulum movementwithout a` braking action on the part of the resilient means x7. Qnly-upon further bending occasioned,for instance,by fasterwalking, the buffer will bemore or less strongly compressed and will nally resiliently limit theswinging movement, forcing the shank to reverse its movement. i

Since it. is desirable ithat the 'shank be not moved toward the outstretched condition by gravity, while the bending is between 160 and 180",` but that bending be favored, I provide, according to the invention, a tension element 8, such as a rubber band or a spring. Such a tension element extends, for instance,- between the shank 3 and the rod2 so as to f orce the thigh, by means ofthe link 9, to bend until the bufferf7 abuts against the guide 6, as shownin Fig. 2.

The,rod 2 is linked to the kneey portion 1 of'thezthigh so that with a bend of more than 90, the point of connection moves to the other side of the center of rotation, as shown inFig. 3. Then, the expansive'forcesof the butter 7 will favor a still further bending of the thigh. This has the advantage that with the bearer being seated, the leg does not tend to stretchout under the `inuence of the resilient means.

The rod 2 is also acted upon by a brakewhich is'preferably mounted on the guide. :The pressure of a small brake shoe is adjusted'by means of a screw.

. In the embodiment shown in'Fig. 4, `the knee` portion 1 of the thigh of an .artificial leg is provided with cam means120, and the shank 3f has jointed thereto a member 22 to guide a compression spring 24, and a support26 for a roller-,28. The .spring bearsat one of its ends upon the support 26 urging the support outwardly. The support is arranged to slide along'the member- 22. The roller 28 serves as a cam follower. `The mechanism of Fig.,4 acts similarly to the swinging control mechanism of Figs. 1 to 3.

In Fig. 5, an auxiliary braking mechanism according to my invention is shown, which; mechanism willrhelp increase the brakingeffect cfa kneep-joint brake, whenever the outstretched leg condition is approached or reached. To the rear end 10 of the brake-shoe 11l of a knee-joint brake, a member 12 is slidably mounted. This member abuts with its upper tlange 413 against the-rear side 14 of the brake lining 15. Atlange` 17 provided with a threaded hole 16 is secured to the brake-shoe11, and a flange 18 issecured to the member 12. The holeY A1li/receives a screw-bolt 19. t It will be understood that on rotating the head 30, the member 12 may be moved against the brake lining to compress same and to increase its thickness.

It is believed that the construction and operation of the forms of the invention, which have been dealt with hereinbefore, and the many advantages fthereof, will be understood from the foregoing detailed description. t Some of the features of theinvention are reviewed hereinafter.

Ashas been explainedthe invention aimsfat the control of the `swinging movements of a leg prosthesis. At therslowestwalking speed, my control. mechanism causes Athe shank to swing easilyand naturally` within the ydesired range, and dur-ing fastestwalking, `the shank is preventedfrom swinging toofar backwards. UIn addition, my control mechanism urges the shank back intothe outstretched leg position.

' It will be apparentthat while I havedealti-primarily with a linkage between the thigh and the shank, articulated-` both` .tonthe vthigh .andthe shank,` and provided .with resilient means, many modifications of the control mechanism fall within the spirit of the invention. For instance, cam and cam follower means may be provided to cooperate together. The cam means are provided on either the thigh or the shank, and-jthecam; follower means on the other leg section. ,The cam follower is urged by means of resilient means with more or less pressure toward the cam to;produce,greaterorrsrnaller friction :during angular movements of the thigh and shankwith respect to one another. The cam'follower may be arranged to roll or to slidefoverthecarn. It LwillA be clear that by proper adjusting of the resilient means, retardation or acceleration of the swinging movements maybe obtained. In order to influence the operation of the resilient connec tion, it is also possible to apply frictional forces at the articulations.

It will alsobe clear that theelectof my controlmechanism may be varied through different positioning of the mechanism, depending onathe location ,of thepointsof application .of ythe forces involved.

Withmy lswinging control .mechanism applied to an artificial `leghaving-l a pressure-controlled knee-joint brake, I- prefer to adjust the brake surface of a kneejoint brake in such a way that whenever the legapproaches or reaches the outstretched condition an increased pressure is exerted onI the corresponding slightly `eccentric brake surface of the thigh. `According tothe invention, this is done-by compressing a brake Alining in eitherlongitudinal and/or transverseY direction-and, thus, increasing its thickness. The device for compressing the brake lining is preferably mounted in the rear of thebrakelining.

' I claim:

1. Leg prosthesis includinga thigh, a shank, a connection between-.the `thighand ;theishank, and elements resiliently atectingand controlling'the relative` angular position of fthe thigh and-shank, said connection includinga rod means,l and a support, the rod.means being articulatedat one endl-to Ithethigh' forpivotal movements, thev support being carriedbyvthe shank and Aslidably `receiving the rod meansnearthe other: end, the resilient elements including a tension member securedat one end to the shank, and at the other end to the rod means, and a body provided on the rodmeans intermediate the ends of the rod means, the resilient elements being provided to rst counterbalance the gravity.tending to move the shank forward, to become more effectiveduring further bending of the shank throughl abending angle up 4to approximately 150, to produce avsteadily increasing counterpressure upon continued bending, and to allow said counterpressure to cease on bending -toan angley of approximately 2. In'the prosthesis according to claimY 1, an abutment carried-by the Vrod means, said body being provided` as a buffer in abuttingrelationship tothe abutment,` and in spaced relationship..to the support in outstretched leg condition, the resilient body abutting against the support in a bent leg condition, and being adapted to becornedeformed on-further bending.

3. `In` theeprosthesis accordingl to claim 1, provided Witha-pressure1controlled yknee-joint brake `including a brake-shoe brakelining anda thigh brake lining, a device movablyarranged to bepressed againstaside ofthe brake-shoe brake `lining to'thicken the latter brake lining and to increase-the friction between the brake linings.

A4. -In the prosthesis accordingito claim l, the rod means being jointed-to the-thigh at a pointlying 4at one side of the center-ofA rotation of the thighand shank up I.toa rotation of approximately 90, the.v said articulation point moving upon further rotation to theothery side ofthe center of rotation.

5. Leg prosthesis. including a thigh, agshank, and a connection between the thigh andthe shank, said connection including cam-means, a camfollowerroller, a guide member, and a compression spring, the cam; means being provided on the thigh, the guide member being articulated to the shank, the cam follower roller being supported by 2,588,013 the guide member to cooperate with the cam means, the 2,679,650 compression spring being housed within the guide member to bear at one end against the cam follower roller.

5 1 12,810 References Cited in the file of this patent 454,142 UNITED STATES PATENTS gg 2,559,017 Hanson July 3, 1951 328,292

6 Kleinekathfer Mar. 4, 1952 Kleinekathfer June 1, 1954 FOREIGN PATENTS Great Britain Jan. 2, 1917 Great Britain Sept. 24, 1936 Italy May 28, 1948 Germany Ian. 17, 1952 Germany Jan. 17, 1952 

